Solar cell boasts world record 44.7% efficiency
Back in May 2013, the German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Centre Berlin had announced a solar cell with 43.6 per cent efficiency. Building on this result, further intensive research work and optimisation steps led to the present efficiency of 44.7 per cent.
These solar cells are used in concentrator photovoltaics (CPV), a technology that achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. The terrestrial use of so-called III-V multi-junction solar cells, which originally came from space technology, has prevailed to realise highest efficiencies for the conversion of sunlight to electricity. In this multi-junction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum.
"We are incredibly proud of our team which has been working now for three years on this four-junction solar cell," said Frank Dimroth, department head and project leader in charge of this development work at Fraunhofer ISE. "This four-junction solar cell contains our collected expertise in this area over many years. Besides improved materials and optimisation of the structure, a new procedure called wafer bonding plays a central role. With this technology, we are able to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. In this way we can produce the optimal semiconductor combination to create the highest efficiency solar cells."
"This new record value reinforces the credibility of the direct semiconductor bonding approaches that is developed in the frame of our collaboration with Soitec and Fraunhofer ISE. We are very proud of this new result, confirming the broad path that exists in solar technologies for advanced III-V semiconductor processing," said Leti CEO Laurent Malier.
Concentrator modules are produced by Soitec (started in 2005 under the name Concentrix Solar, a spin-off of Fraunhofer ISE). This particularly efficient technology is employed in solar power plants located in sun-rich regions with a high percentage of direct radiation.
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